A lavatory unit, a galley, a hand baggage storage shelf, a divider, and the like are arranged inside an aircraft. For example, with respect to the lavatory unit, a housing, which partitions the lavatory, is formed by a plurality of interior panels for an aircraft being joined together. With respect to the galley and the hand baggage storage space, a housing, which partitions the goods storage space, is formed by the plurality of interior panels for an aircraft being joined together, and the divider is formed by the plurality of interior panels for an aircraft being joined together, the plurality of interior panels forming partition plates.
These interior panels for an aircraft, which are used inside an aircraft, are formed by lightweight and rigid panels from the perspective of realizing reduction in weight.
In many cases, such an interior panel is formed by a honeycomb structured core formed of synthetic resin and by surface plates formed of fiber reinforced plastic, reinforced plastic, or metal being adhered to both sides of the core.
Then, when the interior panels for an aircraft are joined together, a metal reinforcing frame having an L-shaped cross-section is arranged at an intersection portion at which the two interior panels for an aircraft intersect, metal insert nuts are embedded in end portions of the interior panels for an aircraft, and metal bolts, which are inserted through attachment holes of the reinforcing frame, are screwed into the insert nuts.
However, with a conventional joining structure as described above, as metal reinforcing frames, metal bolts, and metal insert nuts are used, there has been a disadvantage that the weight of the joining structure increases.
Furthermore, as it is necessary to reinforce sections of the interior panel for an aircraft in which the insert nuts are embedded, the number of parts increases and assembly has become more time-consuming, and there is a disadvantage in terms of realizing cost reduction.